With the progress of the digital technology of electronic devices in recent years, nonvolatile semiconductor memory devices with a large capacity have been actively developed for storing data such as music, images, and information. For example, a nonvolatile semiconductor memory device which uses a ferroelectric as a capacity element has already been used in many fields. In addition to the nonvolatile semiconductor memory device which uses such a ferroelectric capacitor, a variable resistance nonvolatile memory device (hereinafter referred to as a ReRAM) formed by using a material whose resistance value changes in response to an electric pulse application and which holds the state has been attracting attention for the easiness to ensure consistency with a general semiconductor processing.
A nickel oxide (NiO) film, a vanadium oxide (V2O5) film, a zinc oxide film (ZnO), a niobium oxide (Nb2O5) film, a titanium oxide (TiO2) film, a tungsten oxide (WO3) film, a cobalt oxide (CoO) film, or the like is used as a variable resistance layer. It is known that such a transition metal oxide film indicates a specific resistance value when a voltage or current equal to or larger than a threshold is applied and maintains the resistance value until the next application of a voltage or current is provided, and can be manufactured using an existing DRAM processing as it is.
PTL 1 discloses a crosspoint ReRAM in which a memory plug is formed at the crosspoint of an x-direction conductive array line and a y-direction conductive array line. The memory plug includes a variable resistance memory element and a diode element having a metal-insulator-metal (MIM) configuration. The variable resistance memory element is made up of three layers including a lower electrode layer, a complex metal oxide layer, and an upper electrode layer. The diode element is made up of three layers including a metal layer, an insulating layer, and a metal layer. In addition, since an electrode layer that connects the variable resistance memory element and the diode element is provided, the memory plug has a stacking configuration of a total of seven layers.
In addition, PTL 2 discloses a crosspoint ReRAM having a resistance structure and a diode structure between a bit line and a word line.
PTL 3 discloses a crosspoint ReRAM provided with a variable resistance element including a lower electrode, a variable resistor, and an upper electrode between a bit line and a word line, and a nonlinear element connected in series to the variable resistance element.